Armored metal file band and production thereof

ABSTRACT

File band stock and production thereof, comprising: a flexible base metal strip having over at least a surface portion thereof, a strong, tough and adherent, abrasive armoring coating produced in situ from abrasive particles of hard, high melting material selected from the group consisting of metal carbides, borides, nitrides, silicides and combinations thereof, and particles of a matrix metal, said matrix metal particles being in said armoring coating, fusion bonded to each other, to said base metal strip and to said abrasive particles, and partially embedding and anchoring said abrasive particles therein with said particles projecting therefrom in the form of a series of sharp cutting edges, said armoring coating being preferably applied to said base metal strip in spaced regularly recurring pattern areas longitudinally of said strip.

United States Patent [1 1 Dawson et al.

[451 Nov. 27, 1973 ARMORED METAL FILE BAND AND PRODUCTION THEREOF [73]Assignee: Remington Arms Company, Inc.,

Bridgeport, Conn.

[22] Filed: Oct. 15, 1971 [21] Appl. No.: 189,786

Related US. Application Data [63] Continuation of Ser. No. 803,561,March 3, 1969,

2,866,698 12/1958 Kuzmick 51/308 2,906,612 9/1959 Anthony et al. 51/3093,042,508 7/1962 Haictis et a1 51/295 Primary Examiner0thell M. SimpsonAttorney-Raymond J. McElhannon et al.

[5 7] ABSTRACT File band stock and production thereof, comprising: aflexible base metal strip having over at least a surface portionthereof, a strong, tough and adherent, abrasive amoring coating producedin situ from abrasive particles of hard, high melting material selectedfrom the group consisting of metal carbides, borides, nitrides,silicides and combinations thereof, and particles of a matrix metal,said matrix metal particles being in said armoring coating, fusionbonded to each other, to said base metal strip and to said abrasiveparticles, and partially embedding and anchoring said abrasive particlestherein with said particles projecting therefrom in the form of a seriesof sharp cutting edges, said armoring coating being preferably appliedto said base metal strip in spaced regularly recurring pattern areaslongitudinally of said strip.

6 Claims, 14 Drawing Figures Patented Nov. 27, 1973 4 Sheets-Sheet lINVENTORS Chest ev H. Dawson L Robert T Coili'n 8' BY Phillp R HaskellHTTO N EI'S Patented Nov. 27, 1973 3,774,355

4 Sheets-Sheet 2 n @b INVENTOE5 Chester H. Dawson 9 Robert T. Catlin 8'Q'TTO R N EYS em Philip R Haskell g WMWZCM M W Patented Nov. 27, 19733,774,355

4 Sheets-Sheet 3 U INVENTOES Chester H. Dawson Qober c T CaHLn 8' B'fPhilip R. Haskell RTTORNEYS ARMORED METAL FILE BAND AND PRODUCTIONTHEREOF This is a continuation, of application Ser. No. 803,561 filedMar. 3, 1969 now abandoned.

This invention pertains to armored abrading tools and the productionthereof, comprising a structural base member composed of a base metal,such as steel, alloy steel or other metal or alloy characterizedinherently by high strength, hardness and toughness or heat treatable tosuch, said structural base member having a hard wearing, ductile andabrasive surface coating produced in situ from powdered metal particlesof a hard, refractory, brazing or matrix metal or metal alloy, such as anickel-base or cobalt-base alloy, and abrasive particles of a hard, highmelting material, such as metal carbides, borides, nitrides, silicides,or equivalent diamond substitute materials, said matrix metal particlesbeing fusion bonded to each other, to said abrasive particles and tosaid base metal, and said abrasive particles being partially embedded oranchored in said matrix metal and projecting therefrom to provide amultiplicity of sharp cutting edges.

The invention provides a new tool of the above type and methods ofproducing the same, having a new field of utility, namely, flexiblesteel or steel alloy file band stock and bands thereof having surfaceportions armored as above, which are particularly adapted for high speedsurface filing in standard band saw machines, of such refractorymaterials and metals as: glass, fiber glass, ceramics, cement asbestos,tiles, high temperature alloys, such as chrome-nickel alloys, titaniumand titanium base alloys and the like.

Although flexible grinding belts are well known as constructed, forexample, of an abrasively coated paper, cloth or other organic basestrip material, they are commonly used only for surface grinding ofrelatively soft materials, such as wood, or other cellulosic products,unreinforced plastics, relatively soft metals such as aluminum, brass,mild steel and the like. Such belts are, moreover, of relativelyshort-lived utility, as the abrading particles, whatever their nature ormode of bonding to the base or substrate material, are soon dislodgedand broken away in use with consequent loss of grinding action.

Owing to the recognized deficiencies of such belts in the surfacegrinding of harder materials, resort has been had to conventional filebands for such applications, but these likewise are best adapted for thesurface grinding or filing of relatively soft metals, such as aluminum,brass, copper, unheat-treated steel, etc. Moreover, they are of suchcomplicated construction as to be safely operable at only relatively lowspeeds and are fragile and hazardous in operation at best. Where arelatively high degree of accuracy and flatness is required, file bandsarepreferred over grinding belts. Conventional file bands as used onstandard band saw machines are made by riveting short, heavy and rigidindividual file segments to a flexible steel band. A I

locking slot and rivet head is used to join the band ends into acontinuous loop. There are a number of disadvantages inherent in thisconstruction. A relatively short foot length of standard file bandconsists of the following number of parts: One flexible spring steelband, 38 file segments, 38 spacers, 76 segment rivets, two dowel rivetsor 155 parts in total. The maximum recommended velocity for a standardfile band is about 150 ft./min. If this speed is exceeded, the heavyindividual file segments may be torn loose from the spring steel band bycentrifugal force as they travel around the drive wheels of the band sawmachine. If a standard file band is inadvertently mounted in the wrongdirection, it may be seriously damaged as well as create a definitesafety hazard for the operator. The multiple piece riveted constructionof a standard file band forms a large number of stress concentratingpoints with the resultant reduced fatigue life. Since a conventionalfile band ismade up of 3 inch long, individual file segments, theoverall length must be a multiple of these segments. If the band breaks,a special repair kit is required to splice and rivet in a new section.Also, the conventional file band must be ordered directly from themanufacturer in a length specified to fit a definite model of band sawmachine. The individual sections of a conventional file band areessentially the same as conventional files, consequently, its use islimited to relatively soft materials such as unheat-treated steel,brass, aluminum, unreinforced plastics, and the like.

The above-mentioned limitations, complications and drawbacksof'conventional grinding belts and file bands as above discussed, arecompletely eliminated with the armored file band construction of thisinvention, which in addition, has fields of utility which suchconventional tools-do not, namely, for the surface grinding or filing ofsuch refractory materials as: glass, fiber glass, ceramics, cementasbestos, tiles, high temperature alloys, and other metals generallyhaving high hardness inherently or as heat treated for use.

Since thefile bands of the invention contain no rigid file segments, butare flexible throughout, they may safely be operated at speeds of up toabout 3,000 ft/min. with consequent increased grinding efficiency. Thetungsten carbide or equivalent abrading particles being partiallyembedded or anchored in a high strength matrix metal, which in turn ispermanently bonded to the flexible base metal steel or alloy steelstrip, are generally not torn loose or dulled in use. Moreover, thefiling surface in general remains clean in operation and is not cloggedwith abraded material as occurs with conventional file bands. To theextent that clogging-does occur with the file bands of the invention,they can easily be cleaned by the action of a wire brush or withchemicals or solvents which would disintegrate and destroy conventionalgrinding belts of paper, cloth or other organic materials. Particularlywhen filing friable materials like glass or ceramics, it is veryunlikely that clogging will occur with the file band of the invention,in contrast to conventional file bands which have a positive rake andthe individual file segments of which do not flex and hence which do notundergo the automatic cleansing action of the flexible file bands ofthis invention. To the extent that clogging does occur with the flexiblefile bands of this invention, the abrasive particles will still projectand effect an abrading or filing action.

The armored file band stock of the invention being, furthermore, ofunitary and flexible construction throughout its length, may be cut toany length and the ends joined into a loop by a simple welding operationto fit any band saw machine as required. Also, if any particular sectionof the file band becomes damaged, the damaged section may be quickly andeasily cut out with hand shears and a new section welded in its place.Also, the armored file bands of the invention may be run in eitherdirection, in contrast to the required unidirectional operation ofconventional file bands. In addition, the unitary file band constructionof the invention has no points of stress concentration, as in conventional file bands.

More particularly, in accordance with a preferred construction accordingto the invention, the armoring is applied to the base band stock overlongitudinally and optionally also over laterally spaced pattern areasfor assuring good flexibility and fatigue life of the armored bandstock, and for providing unarmored areas for welding the material intobands. Such unarmored areas also function to provide spaces for thecut-off particles of the filed material to be carried out of contactbetween the file band and the work piece and thus prevented frominterfering with the filing action. In addition, in accordance with afeature of the invention, the annoring coating is preferably so appliedby the method described below, that the abrading grit particles areanchored in weldments of the matrix metal which are individual theretoand which may be spaced apart as desired for further enhancing theflexibility and fatigue life of the armored band stock. If the abradinggrit particles are anchored in too close a proximity to one another,dissimilar cooling rates between these particles and the base stock mayproduce warpage of the base band stock or locked-in, undesirablestresses resulting from a tendency to warp.

A preferred method according to the invention for applying the armoringcoating to the substrate band stock, and which also is of generalapplication for armoring tools of other types, consists first inprecoating the abrasive particles with a fluxing agent, such as borax,and with the brazing metal powders in the manner hereinafter described,the brazing metal powders being advantageously of much smaller particlesize than the abrasive particles. A thin adhesive coating is nextapplied to the surface portion or portions of the substrate to bearmored, preferably by a printing operation, employing printers ink orother adhesives as the coating materials, as described below. Beforethis coating becomes dry, the so-printed surface of the substrate ispassed next beneath a falling curtain of the precoated abrasiveparticles at a rate of application adjusted to provide a preselectedaverage spacing between theparticles falling upon and adhering to theprinted surface portions, non-adhering particlesbeing removed thence byan air blast. In this way, the precoated abrasive particles may beapplied to the printed surface portions in as dense or sparse adistribution as desired, depending on the character of the substratebeing armored. For armoring the band file stock of the invention, arelatively sparse distribution is desired for reasons above mentioned.

The thus armored tool or substrate band stock is then allowed to travelfor some distance or through a drying unit until the adhesive coating isdied by removal of moisture therefrom and thence is passed next throughan induction heating coil energized from a high frequency alternatingcurrent source for rapidly heating the tool or file band stock totemperature sufficiently high to melt the brazing metal powders coatingeach grit particle whereby the molten matrix metal flows about the baseof each grit particle and onto the base metal substrate and by capillaryaction coalesces into a cup-like molten pool partially immersing thegrit particle therein, with said particle projecting therefrom.

The extent of this immersion is determined by the amount of brazingmetal particles precoated onto the surface of each grit particle whichis proportioned in accordance with the invention to provide only partialimmersion of the grit particles therein. The extent of immersion of thegrit particles is also controlled by the product of time and temperatureoccuring during brazing. Too high a temperature for too long a time canproduce total immersion of the grit particles, while too low atemperature for too short a time can produce an insufficient and brittlefillet. The tool or file band stock is next subjected to rapid coolingin an inert atmosphere until cooled to temperature such that the moltencup of brazing metal surrounding the base of each grit solidifies andthus permanently anchors the grit base therein in bonded relation to thegrit particle and to substrate base metal. This heating and cooling mayalso be such as to austenitize and thence transform to martensite themicrostructure of the steel substrate which is thereafter subjected to atempering treatment as described below. An alternative albeit lessdesirable procedure is to perform only the brazing operation in theinduction heating coil, followed by an air cool and thence in a separateheating unit, heating the band stock to an austenitizing temperature,followed by quench and temper treatments.

Numerous advantages result from thus individually precoating the grits,each with its own supply of brazing metal and fluxing agent The amountof brazing metal for each grit particle can be accurately controlled topartially embed the same only to an extent desired and to assure thateach grit particle will project therefrom to provide a sharp, exposedcutting edge. The brazing metal for each grit particle bonds only to thegrit particle coated thereby and also only to a relatively small area ofthe substrate base metal. This is of particular advantage in armoringapplications requiring a flexible substrate with optimum fatigueproperties as in the file band of the invention, and also as applied toband saws, sanding discs and the like. This is further facilitated bythe fact that the precoated grits may, as stated, be ap plied to thesubstrate with a controlled average spacing between grits such that thebonded grits may be spaced apart sufficiently as not to impair theflexibility and fatigue life of the substrate band stock. The precoatingalso facilitates application of the armoring coating in spaced patternsin accordance with the preferred embodiment, whereby unannored areas areretained to permit of welding sections of the band stock into bandssuitable for use in standard band saw machines. The precoating of thegrit particles is particularly efficacious where such particles arerelatively large. Small grit particles are, however, more difficult toprecoat and with respect to such, a satisfactory file band can beproduced without precoating.

The advantages resulting from precoating the grit particles are lessreadily obtainable with other methods for applying an armoring coating,such as that wherein there is first applied to the substrate a thinlayer of paste flux, then a layer of the brazing metal powders andfinally an overlayer of the carbide grits, or that wherein a paste fluxand the brazing metal powders are premixed and applied as an initialcoating on the substrate base metal and an overcoating of the gritparticles superimposed thereon. Such techniques tend to produce a layerof brazing metal which covers the substrate in varying the thicknessthroughout the armored at 13, each of said particles 'in and bonded to asubstantially meniscus shaped anarea, depending on the amount of brazingmetal initially applied and wherein it is difficult to control'theextent of embedment of the grit particles. Also, where a flexiblesubstrate is required, as in the case of the file band, the continuouslayer of brazing metal reduces the flexibility and fatigue life becausethe physical properties of the brazing metal may not be compatible withthose of the substrate. Also, the procedure for applying the flux,brazing metal and grit particles in two or three separate operationsresults in increased labor costs, while the excess braze metal notactually employed for anchoring the grit particles increases thematerial cost as compared to the grit precoating technique of thisinvention.

Having thus described the invention in general terms,

reference will now be had for a more detailed description to theaccompanying drawings, wherein:

FIG. 1 is a plan view of a fragmentary portion of steel or alloy steelflexible strip stock which is continuously armored on one surfacelongitudinally thereof, in accordance with one embodiment of theinvention;

FIG. 2 is an enlarged sectional view of FIG. 1 as taken at 2-2 thereof;

FIG. 3 is a plan view similar to FIG. 1, wherein the base stock isarmored in spaced rectangular areas with the armoring coating accordingto a more preferred embodiment of the invention;

FIGS. 4, 5 and 6 are plan views similar to FIG. '3 but showing variousother preferred patterns of the armoring coating applied to the steelbase stock;

FIG. 7 is a diagrammatic showing in flow sheet form illustrative of amethod and apparatus for producing the armored grinding stock of any ofFIGS. 1-7, inc., but more particularly that of FIG. 3;

FIG. 8 is a view in longitudinal, sectional elevation of a non-oxidizingatmosphere cooling and quenching apparatus employed in the flow sheetarrangement'of FIG. 7; while FIG. 9 is a transverse sectional view inelevation through the quenching apparatus of FIG. 8, as taken at 99thereof;

FIG. 10 is an enlarged diagrammatic view in elevation of the essentialcomponents of a strip'drive and printer assembly forming part of theapparatus of FIG.

7, while FIG. 11 is a perspective view of the printer unit as employedin the FIG. 7 flow sheet for producing armored band stock in accordancewith the invention;

FIG. 12 is an enlarged view in elevation of a tungsten carbide particlecoated with a flux such as boraxand matrix metal particles; while FIG.13 is a view in elevation of the coated carbide particle of FIG. 12after fusion bonding to the base metal strip;

FIG. 14 is a diagrammatic view in side elevation of a band saw machineentraining an armor coated grinding band in accordance with theinvention, forsurface grinding a work piece in the manner illustrated.

' Referring to FIG. 1, a flexible strip of a base metal, such as a steelor alloy steel strip 10, is provided with an armoring coating 11extending continuously thereof in the longitudinal direction. Referringto FIG. 2, the armoring coating comprises a myriad of tungsten carbideor other diamond substitute abrasive particles, as being partiallyembedded choring layer as at 14, of a matrix metal,such as a'highmelting, refractory, nickel-base or cobalt-base alloy,

to the base stock 10 over :gular areas as at 16, 17 thereof. FIGS. 4 to6, inc., illusentire-strip with a thin hopper and the which anchoringlayer of matrix metal is in turn bonded to and alloyed with the basemetal 10.

Referring to FIG. 3, the armoring coating is applied longitudinallyspaced rectantrate by way of example, various other spaced patternarrangements in which the armoring coating may be applied to the basemetal strip stock as at 18, 19 and 20.

Advantages of employing these spaced pattern dispositions of thearmoring coating, as shown in FIGS. 345, inc., as compared to thecontinuous application of the armoring coating throughout the length ofthe strip, as in FIG..1, are that the pattern arrangement gives improvedfatigue life to the abrasive band stock and it also provides uncoatedareas between the pattern areas to facilitate welding of ends of theband stock into a continuous loop. The continuous armor coatingarrangement of FIG. 1 may, however, be of advantage for use inhand filesused with some materials, particularly inch thick X 1 inch wide ismounted on an unwind reel 30. By way of example, this coil may containapproxi- -mately 1,000 feet-of strip. A frictional drag mechanism 30.

of conventional construction (not shown) restrains the unwi-ndreel fromturning prematurely in response to the spring energy contained in thewound up steel strip. T-hestrip passes thence between a pair of rubbercovered rolls 31, 32, which frictionally engage the strip and the upperroll of which is driven in order to move it forward against theresistance of the frictional drag mechanism. Thus, the upper roll 31 isdriven by a variable speed electric motor 33 and geared head speedreducer "34, as described more in detail below, while the lower roll--32 functions as an idling back-up roll.

The strip then passes between a pair of rolls 35, 36 of an industrialroll type printing machine, shown gen- "erally at 37 as hereinafterdescribed. This machine prints a desired pattern as shown, for example,in any of 'FIGS. 1-6, inc., on the top side of the strip using a viscouscoating medium, as hereinafter described. The printing machine is drivenvia a chain drive 38 by the same motor and speed reducer 33, 34 thatpowers the drive wheel 31 so that the printing speed and strip speed aresynchronized as hereinafter explained. While the'printed' pattern isstill wet, the strip passes under a vibratory'feed hopper 39,electromagnetically actuated in conventional fashion. This feed hoppercovers the layer as at 40, of tunsten carbide or other abrasiveparticles which have been precoated with a suitable flux such as boraxand the brazing metal powders, as described below. The strip coveredwith the thus precoated tungsten carbide particles travels next past anair blower 41. This blower removes the abrasive particles from all areasof the band other than those which stick to the printed pattern.Depending on such factors as strip speed or spacing between the feed airblower, it may be necessary in some instances to include a dryer betweenthe hopper and the-air blower. Alternatively such a dryer, for exampleasan infra-red ray drying unit, may be disposed as at 42, followingpassage of the strip past the air blower 41.

The strip with the abrasively coated pattern passes next through a highfrequency induction coil 43 energized from a high frequency currentsource 44, as for example of about 5.2 megacycles per second. This coilheats the strip to approximately 1,900 F. to austenitize the steel ofthe substrate strip and to braze the tungsten carbide grit to the stripby causing the steel band to be inductively heated, this heat then byinduction and radiation causing the matrix metal particles coating eachcarbide particle to melt and flow to and about the base of each particlein the manner shown in FIG. 2, as is more fully explained hereinafterwith reference to FIGS. 12 and 13. The strip passes next through anatmosphere chamber 45 and thence through a slotted, water cooled, chillblock 46 extending therefrom as hereinafter described with reference toFIGS. 8 and 9. As the strip passes out of the magnetic field of theinduction coil and into the atmosphere chamber, the matrix metal coolsand solidifies thereby permanently to anchor the grit particle thereinand to band the matrix metal to the grit particle and to the base metalsubstrate. The chill block further cools the heated strip quickly totemperature below that of martensitic transformation of the steelsubstrate, thus to quench harden the same. The chill block is notrequired where the strip stock is made of a steel which hardens on aircooling from the austenitic state.

As discussed more fully below, the atmosphere chamber is supplied with acirculating flow of nitrogen gas to minimize scaling or oxidation of thesteel strip substrate until it is cooled below scaling or oxidizingtemperature. The strip passes out of the chill block 46 through a slot47, thence over an idler support roller 48 and through a tempering oven49, wherein the strip is tempered at about 950 F. The strip passes nextpast of counter 50, which continuously records the total length in feetor otherwise of the strip processed. The strip is next engaged by atake-up reel 51 driven by a motor 52. The take-up reel exerts only anintermittent pull on the band. It is intermittently activated by atension arm 52a resting on the band stock 10, and applies tension whenneeded for coiling but avoids excessive pull which could stretch thefile band at the point where it is red hot and weakly plastic in theinduction heating coil.

Referring to FIGS. 7, 8 and 9 the atmosphere chamber 45 comprises arectangular housing consisting of a base plate 53, and side walls 54,55, made preferably of cement asbestos such as that sold under the tradename Transite." The three-sided structure thus formed is closed at thetop by a laid on glass plate 56. The housing is partitioned into achamber 60 by end and partitioning walls 61, 62, which are centrallyslotted, as at 63, 64 for passage of the armored strip in the directionof the arrow thereon. The housing is provided at its base with an inletpipe 65 for introducing nitrogen gas under pressure which flows asindicated by the arrows in chamber 60, and escapes through the stripfeed slots 63, 64. The portion flowing through strip inlet slot 63 flowsthrough and about the induction heating coil 43 and thus protects thestrip 10 against oxidation as it is heated up by this coil. The portionflowing through the strip outlet slot 64 flows in turn through a slotextending through the chill block 46 in the manner and for the purposesas follows.

Referring to FIGS. 8 and 9, the chill block comprises a pair ofsubstantially rectangular chill blocks 70, 71, made of metal of highthermal conductivity, such as copper or aluminum. These blocks arebolted together as at 72, 73 and supported on the base plate 53 of theatmosphere chamber housing and are otherwise mounted between the sidewalls 54, 55 thereof, with the glass cover plate 56, disposed inpartially overlapping relation to the upper chill block as shown. Thechill blocks are longitudinally slotted medially thereof, as at 75, 76to provide a passageway as at 77 for feeding the bank stock 10therethrough. Within this passageway are disposed angle members, as at79, 80 made preferably of the aforesaid Transite cement asbestos. Theseangle members are supported on the lower chill block 71 as shown in FlG.9, and the band stock 10 is in turn slidably supported on the upperhorizontal surfaces of the angle members. The primary purpose of theTransite supports 79, 80, is to center the band stock 10 in the chillblock passageway 77 for more uniformly cooling the band stock. Thus, byvirtue of these Transite supports, the file band 10 is not asdrastically quenched in passing through the chill block passageway 77 asit would be if permitted directly to contact the chill blocks.

The side wall 55 is penetrated by a pipe connection 81 which connectswith a passageway 82 formed of semicircular grooves machined in theupper and lower chill plates, as at 83, 84, this passageway extending toan opening into the strip passageway 77, in the manner shown at 83, 84in FIG. 8. Nitrogen gas introduced under pressure through the pipeconnection 81, flows through the passage 82 and into and through thefile band passageway 77 to its exit end. Also, the portion of thenitrogen gas introduced into the atmosphere chamber 45 which flowsthrough the file band exit slot 64, also flows through the strippassageway 77 to the exit end thereof. The nitrogen gas flow is thusdirected along both the upper and lower surfaces of the file band andthus prevents oxidation thereof as the band is being cooled below thatof martensitic transformation. The glass cover plate 46 is loosely laidon the atmosphere chamber to avoid strain from differential heating thatwould otherwise occur if clamped in place.

Each of the chill blocks 70, 71, is longitudinally bored, as at 90, 91,these bores extending from openings at one end thereof, as at 92, 93,FIG. 8,'but terminating short of the opposite end, as at 94, 95. Theseclosed ends are connected respectively by bores normal thereto, as at96, 97, which extend through the chill blocks and thence through theside wall 54, of the atmosphere housing, where they are joined by a U-shaped tubular coupling 98. The open ends 92, 93 of the bores 90, 91,are tapped to pipe fittings, as at 99, 100, comprising inlet and outletconnections for circulating flow of coolant liquid, such as cold water,from an inlet connection, such as 99, thence in order through bores 91,97, through coupling 98 and bores 96, to the outlet connection 100. Inthis way, the chill blocks are maintained at temperature sufficientlylow to effect the desired quenching action of the file band stock as itis fed through the passage 77.

The printing unit 37 of FIG. 7 being of conventional construction, isshown diagrammatically in its barest essentials in side elevation inFIG. 10, and in perspective in FIG. 11. Referring thereto, the motor andgeared head speed reducer 33, 34 drives the upper feed roll 31 to feedthe steel substrate strip stock 10 in the direction of the arrow.Mounted on the shaft of the feed roll 31, is a sprocket encircled bydrive chain 38, which also extends about a sprocket 111 of the samediameter, mounted on the shaft of an inking roll 112 which is thusdriven in the direction of the arrow thereon by the feed roll 31. Theinking roll dips into a bath 113 of a viscous coating liquid, such, forexample, as printing ink, contained in a well 114. The ink roll 112 isgeared with a 1:1 ratio to the shaft of an intermediate, rubber coveredinking roll 1 of the same diameter as roll 112. The intermediate inkingroll 115 is geared with a 1:1 ratio to the shaft of a printing roll 35of the same diameter. The printing roll has embossed thereon as at 117,the armoring pattern to be printed on the band stock 10, such forexample, as any of the patterns illustrated in FIGS. 1 and 3-7, inc.,among others, that shown in FIGS. 10 and 11 corresponding to the patternof FIG. 3. The print roll 35 lightly engages the upper surface of thestrip stock as describedbelow, the strip at the point of engagement withsaid printing roll, passing over an idler back-up roll 36.

Thus, as the printer is driven as above described, the inking roll 112which is continuously coated with the coated liquid from bath 113,progressively applies the same to the intermediate inking roll 115,which in turn applies the liquid to the embossed pattern 117 of theprint roll 35, whichin turn progressively prints the pattern on to themoving file band strip, as at 119. Since all of the rolls 112, 115 and35 of the printer are of the same diameter and are geared to one anotherwith unity ratio gearing, and since the feed rolls 31, 32 are likewiseof the same diameter as the printer rolls and are geared at unity ratioto the printer rolls via the chain drive and sprockets 38, 110, 111, theprint roll 35 will be driven at the same surface speed that the strip 10is fed.

Referring to FIG. 11, the housing 120 of the printer has extending fromits far end, a shaft 121, the opposite ends of which are joumalled tostanchions, as at 122, whereby the printer unit is pivotally supported.At its near end, the housing 120 has secured thereto, an angle member123, through which is tapped an adjusting screw 124, the lower end ofwhich bears against a fixed support 125. Thus, by appropriatelymanipulating the adjusting screw 124, the pressure exerted by the printroll 35 on the band stock 10 may be so adjusted that the print rollprints the viscous coating liquid onto the band stock 10 in patternedareas which are precisely in accordance with the embossments 117 of theprint roll, and in the manner shown at 119, with no overflow along theedges of the patterned areas but with the coating applied unifonnlythroughout the printed areas.

For applying extremely viscous coating liquids, the rolls of the printerare arranged as shown in the drawings, wherein the dip roll 1 12 coatsfirst the plain, rubber covered roll 115, and wherein the latter roll isadjusted out of surface-to-surface contact with the dip roll in orderthat the plain roll l 15 may accumulate and build up on its peripheralsurface a thick coating of the adhesive liquid. The print roll 35 isthen adjusted sufficieritly away from the surface of roll 115, in turnto pick up and carry on its embossed surfaces 117, a rather thickcoating of the adhesive coating liquid. Roll 35 is then adjusted bymeans of screw 124, until its embossed surfaces pass nearly in contactwith the upper surface of the band stock 10 as roll 35 rotates. Theseadjustments prevent a squeezing out of adhesive coating liquids whichare relatively slow drying and very viscous.

For printing with fast drying coating liquids, the print roll 35 and theplain roll 115 may be interchanged, so that the dip roll 1 12 firstcoats the embossed areas 117 of the print roll 35, which in turn printsthe coated areas thereof onto the plain roll 115, which in turn printsthe so-coated areas thereof onto the band stock 10 by an offset printingoperation.

The coating liquid may be conventional printers ink minus the coloringmatter, compositions for which are described in standard texts, such asChemical and Metallur gical Engineering 47.544 (I940), KingzettsChemical Encyclopaedia, 1940 Ed., page 520, and Shreves Chemical ProcessIndustries, I945 Ed., page 509. As statedin these publications, printingink consists essentially of a suspension of pigments, such as paintpigments, in a drying oil, such as linseed oil, or petroleum oils, towhich may be added various natural or synthetic resins, waxes, gums,water insoluble soaps, driers, antioxidants, bitumen, asphalt or stearinpitch,

etc.

In addition to the conventional printing inks, applicants have found thefollowing adhesive printing admixtures to be suitable for purposes ofthis invention.

EXAMPLE I Admix 7 /2 oz. Nicrobraz Flux, 8O milliliters Corn Syrup, IOmilliliters Lube Well D-lOO, water soluble oil used as an emulsifier andto promote wetting, 2O milliliters ethylene glycol to slow up dryingaction, and 25 milliliters water. This mixture is suitable for use in aprinting unit arranged as shown in the FIGS. 10 and 11 drawings and asabove described with reference thereto.

EXAMPLE II Admix 7 oz. Nicrobraz Flux with milliliters glycerin.

The flux is used in the above examples as the solid in suspension toprevent squeegee action during printing which otherwise causes theadhesive to push out around the print pattern thus destroying theprecise pattern. The addition of extra solids makes room between theprinter and the surface being printed so that an adequate thickness ofadhesive material may be applied. Flux'is compatible with the processwhere many other types of solids for the purpose leave harmful incusionsin the finished product. The Nicrobraz Flux referred to in the examplesis a boride-fluoride flux put out under that designation by the WallColmonoy Company, Detroit, Mich.

As above stated, the preferred material applied to the steel or alloysteel base metal band stock for purposes of armoring comprises tungstencarbide particles precoated with a suitable flux, such as borax, andalso with the brazing metal powders. The materials employed for thebrazing metal are preferably powders of hard, refractory alloys, such asnickel-base or coblat-base alloys, capable of providing a matrix metalwhich wets the surfaces of and bonds to the tungsten carbide or otherdiamond substitute particles and also which fusion bonds to and alloyswith the steel or alloy steel base metal band stock. Suitable suchbrazing alloys are Stellite, a cobalt-chromium tungsten alloy of wellknown composition; also that sold by the Wall Colomony Corporation, asLM Nicrobraz comprising an alloy consisting of 13.5 percent Cr, 3.5percent B, 4.5 percent Si, 2.5 percent Fe and the balance nickel. Asuitable particle size for the brazing metal powders is 300 mesh. Asuitable particle size for the carbide particles is that which passesthrough a 30 mesh screen but is held on a 40 mesh screen. Thus, theparticle size of the carbide particles is considerably greater than forthe brazing metal powders.

The following is a suitable procedure for precoating the tungstencarbide or other abrasive grit particles with a iluxing agent and withthe matrix metal powders, although the proportions given below may bevaried within fairly wide limits with satisfactory results. Assumingtungsten carbide grit of relatively coarse grit size, for example 30-40mesh, is required, the procedure is to admix in a containerapproximately 1 lb. tungsten carbide grits, 1.4 oz. Oxweld Brazo Flux(botax), 4 oz. 300 mesh braze alloy granules and 50 ml. water. Whererelatively fine (70-l00 mesh) tungsten carbide grits are required, anadmixture in approximately the following proportions is suitable, 1 lb.tungsten carbide grits, 1.4 oz. Oxweld Brazo Flux (borax), 4 oz. 300mesh braze alloy granules and 65 ml. water. In either case, the water isboiled off until a thick slurry is formed while stirring continuously tokeep the solids from sticking to the bottom and sides of the container.The slurry is then spread on a flat surface and trowelled to a thicknessof three-sixteenths inch, which is sliced into small squares and allowedto dry to a solid cake. The dry cake is crushed and screened through asieve of a mesh adapted to pass single tungsten carbide grits coatedwith brazing alloy, but not to pass a multiplicity of such grits stucktogether. The larger crushed dry cake particles retained on the sieveare recrushed and rescreened. This procedure is repeated until all ofthe dry cake particles are crushed adequately to pass through the sieve.Any excessive braze alloy granules which do not adhere to the tungstencarbide grits are screened out on a sieve size substantially smallerthan the coated tungsten carbide grits. The adherence of the brazingalloy granules to the tungsten carbide grits may be improved by gentlyhand mixing shellac with the small dried cake squares prior to crushing.For this purpose, approximately 12 milliliters of shellac may suitablybe used for each pound of coarse (30-40 mesh) tungsten carbide grits inthe original mixture, or 15 ml. of shellac for each pound of fine(70-100 mesh) tungsten carbide grits in the original mixture. After theshellac dries, the remaining procedure is the same as above described.

A so-coated carbide particle is shown in enlarged view in FIG. 12,wherein the grit particle is shown at 130, the flux coating at 131 andthe brazing or matrix metal particles at 132. As the so-coated carbideparticle passes through the high frequency induction coil, the matrixmetal powders become molten and under the fluxing action of the boraxand flow to and about the base of the carbide particle and against thebase metal in the manner illustrated in FIG. 13, wherein the carbideparticle is shown at 130, the fused brazing metal at 133 and the basemetal at 134. On subsequent cooling, the matrix metal solidifies andalloys with the base metal and also bonds to the carbide particle,thereby permanently anchoring the base of the carbide particle in thematrix metal, with the carbide particle projecting therefrom to provideexposed sharp cutting or abrading edges, as at 135.

Referring to FIG. 3, in a practical embodiment of the invention, thesteel strip 10 may be made of a suitable grade of heat treatable steelor alloy steel, such as A151 6150, of 1 inch in width and 0020-0035 inchin thickness, and the rectangular armored portions l6, 17 may coverareas of 15/16 inch wide X 0.25 inch in length and spaced apartlongitudinally of the strip preferably by about nine thirty-secondsinch.

A dimensional characteristic which is common to all of the patternedareas of FIGS. 3-6 inc., is a longitudinal separation between successiveareas of each pattern group by about nine thirty-seconds inch, as atA-D, inc. This spacing between groups allows for cutting the band stockwith shears and welding into a loop while retaining the spacing of aboutnine thirty-seconds inch between patterned areas contiguous to theweldment. As above stated, this spacing also provides blank spacesbetween the armored areas in which ground off particles of the workpiececan be carried away and out of the tool workpiece contact area.

Referring to FIG. 14, the armored file-band stock may be employed forfiling applications by forming a section of the stock into a closed bandby welding the opposite ends together. This band, as at 140, is thenspanned over and about a pair of spaced sheaves, 141, 142, with thearmored surface of the band on the outside. The lower sheave 142 or thesheave which pulls the file band through the cut is power driven.Mounted intermediate the sheaves is a work table, as at 143, forslideable support'of a workpiece, as at 144, this table being slotted asat 143a for passage of the file band. For filing the workpiece 144, itis manually forced against the armored band 140. In some applications itmay be found advantageous to mount a back-up block as at 145, on therear side of the file band, the block being bolted to the work table asat 146, to provide a back up for the file band where heavy pressure isrequired for filing the workpiece. During the filing opertion, liquidcoolants may be employed to prevent overheating of the file band andworkpiece.

What is claimed is:

l. A flexible file band comprising: a flexible strip of a hardenable andtemperable steel having over at least a surface portion thereof, astrong, tough, and adherent abrasive armoring coating produced in situfrom abrasive particles of hard, high melting point, refractorymetal-carbides, precoated with particles of a high melting and toughbrazing metal selected from the group consisting of cobalt-base andnickel-base alloys and combinations thereof, said brazing metalparticles being fusion bonded to each other and to said steel strip andalloyed therewith into weldments individual to and partially embeddingsaid abrasive particles bonded to and, with said abrasive particlesprojecting from said weldments to form sharp cutting edges, saidarmoring coating being applied to said steel strip in longitudinallyspaced pattern areas for increasing flexibility and fatigue lifethereof.

2. A file band according to claim 1 wherein said weldments are spacedapart for increasing flexibility and fatigue life thereof.

3. A file band according to claim 1 having unarmored opposite endswelded together to form said band into a continuous loop.

4. A file band according to claim 1 wherein said weldments of fusedmatrix metal comprise about onefourth the weight of the abrasiveparticles partially emranging from about 4:1 to 12:1.

6. A file band according to claim 5 wherein said abrasive particles havean average grain size of about 0.006 to 0.023 inch.

2. A file band according to claim 1 wherein said weldments are spacedapart for increasing flexibility And fatigue life thereof.
 3. A fileband according to claim 1 having unarmored opposite ends welded togetherto form said band into a continuous loop.
 4. A file band according toclaim 1 wherein said weldments of fused matrix metal comprise aboutone-fourth the weight of the abrasive particles partially embeddedtherein respectively for exposing sharp edges of said particles.
 5. Afile band according to claim 1 wherein the average grain size of saidabrasive particles exceeds the average grain size of said brazing metalparticles in ratios ranging from about 4:1 to 12:1.
 6. A file bandaccording to claim 5 wherein said abrasive particles have an averagegrain size of about 0.006 to 0.023 inch.